Voltage dividers are often used in electronics, for example, to provide a voltage that is different from that of an available power source. Some voltage dividers have been designed using resistors. On a semiconductor substrate, commonly utilized voltage dividers use P+ poly resistors created with polysilicon.
However, the use of resistor-based voltage dividers in an integrated circuit (IC) has some drawbacks. For instance, it is difficult to form a resistor with high resistance using polysilicon, which requires a large surface area. Also, the resistance presented by a polysilicon resistor tends to vary with process and temperature changes, thus rendering it unsuitable for certain applications.
Although there have been attempts to create voltage dividers using Metal-Oxide-Semiconductor (MOS) transistors, those voltage dividers operate based on gate tunneling currents. As the inventors hereof have noted, gate tunneling currents are not well modeled and are highly dependent on technology, voltage, and temperature, which disfavor robustness and portability. Other approaches require the employment of special devices such as depletion-mode FET transistors or double-gate FET transistors, which are not commonly available Complementary MOS (CMOS) technologies. To address these, and other concerns, the inventors hereof have developed MOS-based voltage dividers capable of using standard MOS transistors operating in triode or saturation modes.